Flame spraying



July 25, 1967 c. s. BATCHELOR ETAL 3,332,753

FLAME SPRAYING v Filedot. 1o, 196s JK ai United States Patent C) 3,332,753 FLAME SPRAYING Clyde S. Batchelor, Trumbull, and Warren R. Jensen, Stratford, Conn., assignors to Raybestos-Manhattan, Inc., Passaic, NJ., a corporation of New Jersey Filed Oct. 10, 1963, Ser. No. 315,251 3 Claims. (Cl. 2li-191.6)

This invention relates to the flame spraying of substrates with metallic coatings, to the novel method and means for accomplishing the same and to the novel products resulting ltherefrom.

More particularly, the present invention relates to the flame spraying of a substrate which may be a planar, angular or curvilinear base of heat-resistant character such as bodies of metallic, ceramic or mineral-liber character, with a coating of metal of a new and improved character, and it is an object of the present invention to provide metal coatings of the character aforesaid having in-clusions of discrete particles of modifying metal dispersed therein.

In general, the objects of the present invention are accomplished by providing novel composite flame spraying wire composed of a solid metal tube having disposed therein solid wire of relatively soft and lower melting point metal modifying material preferably substantially filling the contines of said tube, the contained wire being also substantially insoluble in the tube metal under llame spraying conditions. The said contained solid wire is disintegrable under ame spraying conditions concommittantly with the tube metal, the latter, together with an air or other gap between the two, in the preferred embodiment of this invention, providing a barrier against substantial alloying thereof with the tube metal.

The composite flame spraying wire of the p resent invention is adapted to be sprayed by conventional llame spray guns at a temperature and at a rate to atomize first the solid metal tube and then contained wire and to me-chanically trap the atomized modifying particle material resulting from the wire inclusion without appreciable alloying or solution lof the solid metal components or their appreciable degradation.

It is presently known to employ llame spraying techniques `and to provide composite deposits of materials such as, for example, ceramics and metallic materials by separately llame spraying the metal from a solid wire with the conventional wire llame spray or metallizing gun, and at the same time spraying lthe ceramic particle material from a different point and at an angle to the llame sprayed from a powder gun. In such operation the metal and the separately sprayed particle material are projected adjacent to each other and not in admixtures except possibly in the overlapping areas of the sprayed -cones resulting from the llame spraying technique.

As distinguished from the prior practices and when employing the composite flame spraying wire of the present invention, greater eiciencies are obtained, that is, loss of sprayed metal and particularly loss of the softer modifying metal, is materially reduced and more uniform mixtures are obtained.

In the present case the spray has a surrounding coating -or conical zone of metallic particles resulting from the metal tube of the composite, and the modifying particles resulting from the wire disposed within the tube tend to be retained within said zone and adjacent the axis of the spray. Thus with the employment of the composite flame spraying wire of the present invention Ibetter and truer mixtures are obtained in an easy and more positive manner as distinguished from layers, since even when spraying two materials simultaneously at an angle to each other it is dif-cult to have both meet, and one component tends to blow the other away, resulting in wastage. This is disr'ce tinguished from the practice of the present invention in which use of the composite wire provides an enveloping and trap-like spray of metal formed from the tube around the sprayed particle material resulting from `the metal wire ldisposed within the hollow of the tube.

Moreover, employment of `conventional spray guns can be operated at a controlled feed rate and temperature such as to melt and atomize the metals, the llame and feed rate being regulated so as to be insuicient to appreciably degrade the contained modifying wire metal or to substantially alloy it with or dissolve it in the metal of the tube.

The provision of the composite llame spraying wire of the present invention is particularly conducive to the production of densified deposits as distinguished from the relatively porous character of the deposits resulting from the flame spraying of solid unitary composition metal tubes. This is believed to result from the fact that the heat generated at the nozzle of the spray gun goes through the wall of the `tube rapidly as distinguished from the requirement to travel through a solid rod, and results in a more uniform distribution of the heat into and through the metal tube. The metal which is atomized and propelled by gas under pressure at substantially the same time that it is melted, due to its having been uniformly heated, apparently has a more plastic flow when the particles thereof land on the substrate enabling these sprayed particles to become deposited in a dense even though mechanically interlocked mass of particles and to provide better anchoring and interlock of the contained softer modifying metal particle material which is simultaneously deposited.

The tube component of the composite wire of the present invention may be composed of metal such as principally of copper, aluminum, or iron, the latter including l steel.

Although in all instances the metal of the tube is of relatively harder, higher melting point than the metal disposed within the confines thereof, where the contained metal is to serve as a lubricant for the relatively harder, higher melting point of the tube, the tube metal should generally comprise at least 50% and preferably 60% and upwards of the total volume of the metals and form the matrix in the deposit.

In some instances the reverse may be the case. Thus, where for example it is desired to obtain the high electrical and heat conductivity of for example copper, and to provide therein reinforcing metal therefor such as iron particles, the tube will be a minor amount by volume of the ferrous metal with for example a continuous length of copper disposed therein forming the major amount by volume, the copper forming the matrix metal in the sprayed deposit.

In the preferred practice of the present invention it is desirable to have a gap, which can remain as an air gap, between the tube and the filling metal to provide an added shield during the flame spraying operation for the relatively softer metal of the contents of the tube. This may be readily accomplished by employing a solid metal wire of lesser diameter than the inside diameter of the metal tube within which it is disposed. As an alternative, the gap may be employed and filled with for example hydrocarbon oil lubricant or a ller of a thickened aqueous material such as a rubber or resin latex or aqueous vegetable gum, sodium carboxy methyl cellulose, an aqueous dispersion of colloidal graphite or the like. Similarly thickened or thixotropic aqueous compositions of materials such as colloidal alumina (Du Pont Baymal), bentonite, china clay and the like may be employed either alone or as a carrier for inorganic modifying particle material, for example 600 mesh silicon carbide.

In a non-fully equivalent alternative, the tube may be entirely filled by casting molten metal such as lead, babbitt metal, silver solder, etc. therein. In such instances the tube should also be heated to prevent solidification of the metal cast within the hollow thereof during filling so as to insure complete filling of the tube.

Thus, for the purpose of improving the machinability of the deposit, a ferrous metal tube, such as one composed of iron, steel, stainless steel and the like, there may be disposed within the tube a minor amount by volume of a relatively softer metal or alloy such as copper, bronze, brass, babbitts, aluminum, and the like, and preferably lead.

As another example, the tube forming the major amount of the metal by volume can be of copper and the metal disposed therein similarly may be lead, babbitt metals, silver solder or silver brazing alloys, soft solder such as lead and tin alloys, and the like, to provide good bearing metals. In this instance the copper tube may in itself be a copper alloy such as of bronze or brass. Tubes of aluminum forming the major amount of the composite metals may also be employed, for example, in bearings where the metal disposed within the aluminum tube is for example tin. The aluminum tube may of course also contain modifying amounts of metals. For example, the aluminum tube may be composed of an alloy of 7% tin, 1% copper, 1.6% nickel, 0.6% silicon, 1% magnesium, 0.6% iron and the balance aluminum. Disposed within this tube can be a solid tin wire.

As another specific example illustrative of the present invention, a babbitt wire composed of 88% tin, 6% antimony and 6% copper and having a diameter of .050 inch was disposed in a copper tube of a 1/s inch outside diameter and a 1/6 inch inside diameter, the copper tube being l82% and the babbitt wire 18% by weight of the total metal. This composite was fiame sprayed from a metallizing gun onto a substrate consisting of steel to provide it with an in situ formed bearing surface. The resultant deposit consisted of small islands of babbitt metal uniformly dispersed in a strong matrix of copper. In service the babbitt plasticizes as a film providing the low friction of babbitt backed up by the rigidity of the copper. The manufacture of such `bearings has in the past been limited to expensive and complicated sintering processes employing sintering technology and has precluded the use of many lubricating materials such as the aforesaid, the lubricating metals in bearings produced by sintering being limited to metals insoluble in the matrix.

The composite flame spraying wire of the present invention is particularly adapted to facilitate the production of bearing surfaces of the aforesaid character and other metallic overlays wherein the inclusions are of lower melting character than the tube or are unstable compounds at the 5000-6000 F. temperature generated by the Oxy-acetylene or other chemical ame of the spray gun, in that firstly the fillers are protected by the metallic sheath, and secondly by the air or other gap, in the preferred form of the present invention.

Thus in dame spraying, the metallic tube melts first and is atomized and hurled at the target piece or substrate along with the atomized filler material which has been in part protected from the heat by both the outer shield of the metal tube which melts first, and the embracing medium or air gap. The method of the present invention thus also permits the inclusion of metals which may alloy with the tube meta-l but because of the short time that the filler metal is exposed to the fiame little or no alloying will take place.

In all instances due to the flame spraying technique employed and the protection and rapid cooling of the particle material on leaving the gun in its passage to the substrate, no appreciable alloying is encountered and the fidelity of both the tube metal and the contained metal wire is substantially retained.

In the accompanying drawings:

FIG. 1 diagrammatically indicates the spraying of a composite flame spraying wire of the present invention onto a fiat substrate.

FIG. 2 is a longitudinal section of the composite ame spraying wire of the present invention.

FIG. 3 is a relatively enlarged view of the end of the nozzle of the ame spraying gun and of the composite wire as it issues therefrom as it is atomized, illustrating the enveloping conical effect of the outer cone of atomized metal and the inwardly disposed issuing cone of atomized modifying metal wire inclusion.

Thus, referring to the drawings, the fiame spraying wire 10 of the present invention comprises a metal tube or jacket 11 which can have an outside diameter of 1/8 inch to fit a standard wire flame spraying gun and suitably has an inside diameter of about j@ inch containing the modifying wire material 12. Spraying of the composite 10 which desirably is flexible and fed from a conventional reel, not shown, is diagrammatically shown in FIG. 1 by means of the nozzle generally indicated as 13 having an air cap 14 together with passages therein comprising the compressed air passage 15 between the air cap 14 and the nozzle part 16. The combustion gas 13 passes between the nozzle parts 16 and 17 which provides an axial orifice for supporting the composite wire 10 while being fed through the nozzle. The sources of combustion gases and compressible propelling gas, i.e. the air supply being part of conventional metallizing guns is well understood and therefore not shown.

The resulting atomized spray 19 initially comprising an outer cone 20 and an inner cone 21 impinges at a right angle to the substrate 22 with high velocity and efficiency and with a better and truer mix than when separately spraying particle material and metal rod at angles converging to the work. In the latter practice one spray tends to blow the other away, whereas in the present method and with our novel composite wire, an enveloping traplike spray of metal from the tube 11 envelope the atomized particle material of wire 12 to provide a high and stable yield and a substantially homogeneous mixed surface coating 23, as distinguished from layers of the components. Although the substrate 22 is shown to be flat it will be understood that it may be curvilinear for parts such as bearings, brake shoes, brake drums, shafts and other curvilinear or cylindrical surfaces, and with such curvilinear surfaces it will be understood that the spray is to be in a general radial direction to the work, such radial projecting -being generally comprehended by the terminology in the following claims and being in a direction normal to the work.

It will be understood of course that when spraying metallic substrates, they are conventionally pre-heated before spraying and suitably cleaned or abraded.

As a further aid in anchoring the sprayed deposit to a tie-ply, i.e. an underlay or dash of spraying metal is first applied to the substrate. An example of this is a silver solder known as Easy Flo 46 which has a melting point of 1160o F. and a flow point of 1175 F. and has the fgllowing composition in per cwt. by weight: 50 silver, 15.5 copper, 16.5 zinc and 18.0 lead.

The tie-ply spray wire may contain flux such as borax or the coating may be painted with a coating of a flux after spraying. The desired overlay is then sprayed to the desired thickness. The entire composite may then be heated to a suitable temperature which, with Easy Flo 46, is between 1200 and 1400 F. to improve the bond. It is sometimes desirable to have a transition area between the tie-ply and the body of the overlay. This can be accomplished by laying down a fiash of the final overlay onto the tie-ply followed by a secondary flash of tie-ply. Y

This produces a gradation of the analysis above the tieply and tends to make the final overlay compatible with the tie-ply.

As an example of the production of hard but relatively machinable deposits, a steel tube of SAE 1080 5 material, having M3 O.D., 1/16" I D. is provided with an inserted lead wire of .040 diameter. This produces a composite analysis of Percent Iron 93.7 Lead 6.3

Another example is silver solder wire in copper tubing to improve bond strength. (Heated to 12001400 F. after spraying.)

Percent 1A X 1/L copper tube 84.0 .050 Easy Flo 46 wire insert 16.0

An example of an aluminum :bearing material which is particularly adaptable for use as applied to aluminum `backing materials or substrates is as follows:

Tube Ms" O.D. X .040 LD. analyzing 1% cu, 1.6% Ni,

.5% Si, 1% Mg and balance aluminum.

Wire insert tin .032" in diameter.

Aluminum alloy tube percent 86 Tin do 14 Another example is an aluminum tube as above of Ms" O D. x .0625 I.D. with ten wire insertion of .032 diameter, threaded with a film of colloidal alumina 25 (Baymal) and 600 mesh crystalline alumina to produce an We claim:

1. Composite ame spraying wire comprised of an inner metal wire and an enveloping metallic sheath, said wire being of smaller diameter than the inner diameter of sheath providing a gap filled with an aqueous fluid composition between said components.

2. The composite of claim 1 wherein the gap is filled with an aqueous colloidal dispersion.

3. The composite of claim 1 wherein the gap is lled with an aqueous colloidal dispersion having suspended therein inorganic modifying particle material selected from the group consisting of ceramic oxides and carbides.

References Cited UNITED STATES PATENTS 1,531,827 3/1925 Armor 219-146 1,738,828 12/1929 Jackson 219-145 X 2,231,247 2/1941 Bleakley 117-1055 X 2,805,317 9/1957 Brillie 219-146 X 3,059,093 10/1962 Norcross et al. 219-145 X 3,254,970 6/ 1966 Dittrich 29-191 X FOREIGN PATENTS 543,773 3/ 1942 `Great Britain.

ALFRED L. LEAVI'IT, Primary Examiner.

A. GOLIAN, Assistant Examiner. 

1. COMPOSITE FLAME SPRAYING WIRE COMPRISED OF AN INNER METAL WIRE AND AN ENVELOPING METALLIC SHEATH, SAID WIRE BEING OF SAMLLER DIAMER THAN THE INNER DIAMETER OF SHEATH PROVIDING A GAP FILLED WITH AN AQUEOUS FLUID COMPOSITION BETWEEN SAID COMPONENTS. 